From ff48a801bf7135ec21aeae56fb63ff9fe66b1f8b Mon Sep 17 00:00:00 2001
From: Peter Birch <pbirch@fractile.ai>
Date: Wed, 1 Oct 2025 11:06:20 +0100
Subject: [PATCH 1/2] Fixing 'utils.unpack(...)' when used against an ArraySpec

---
 packtype/types/array.py      | 12 ++++----
 packtype/utils/basic.py      |  3 ++
 tests/grammar/test_struct.py | 57 +++++++++++++++++++++++++++++++++++-
 3 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/packtype/types/array.py b/packtype/types/array.py
index 834ff2d..7201639 100644
--- a/packtype/types/array.py
+++ b/packtype/types/array.py
@@ -3,6 +3,7 @@
 #
 
 import functools
+import inspect
 import math
 from collections.abc import Callable, Iterable
 from typing import Any, Self
@@ -69,6 +70,11 @@ def as_packed(self, **kwds) -> "PackedArray":
     def as_unpacked(self, **kwds) -> "PackedArray":
         return UnpackedArray(self, **kwds)
 
+    def _pt_unpack(self, packed: int) -> "PackedArray":
+        inst = PackedArray(self)
+        inst._pt_set(packed)
+        return inst
+
     def __call__(self, **kwds) -> "PackedArray":
         return self.as_packed(**kwds)
 
@@ -171,12 +177,6 @@ def _pt_width(self) -> int:
     def _pt_pack(self) -> int:
         return int(self._pt_bv)
 
-    @classmethod
-    def _pt_unpack(cls, packed: int) -> "PackedArray":
-        inst = cls()
-        inst._pt_set(packed)
-        return inst
-
     def __int__(self) -> int:
         return self._pt_pack()
 
diff --git a/packtype/utils/basic.py b/packtype/utils/basic.py
index 1437ec8..22d0c71 100644
--- a/packtype/utils/basic.py
+++ b/packtype/utils/basic.py
@@ -6,6 +6,7 @@
 import math
 
 from ..types.alias import Alias
+from ..types.array import ArraySpec
 from ..types.assembly import PackedAssembly
 from ..types.base import Base
 from ..types.enum import Enum
@@ -120,6 +121,8 @@ def unpack(ptype: type[Base], value: int) -> Base:
     :param value: The value to unpack
     :return: An instance of the Packtype definition with the unpacked value
     """
+    if isinstance(ptype, ArraySpec):
+        return ptype._pt_unpack(value)
     if not inspect.isclass(ptype):
         raise TypeError(f"{ptype} is an instance of a Packtype definition")
     if not issubclass(ptype, Base):
diff --git a/tests/grammar/test_struct.py b/tests/grammar/test_struct.py
index 1dc7748..0fbb18b 100644
--- a/tests/grammar/test_struct.py
+++ b/tests/grammar/test_struct.py
@@ -2,12 +2,14 @@
 # SPDX-License-Identifier: Apache-2.0
 #
 
+import random
+
 import pytest
 
 from packtype.grammar import ParseError, UnknownEntityError, parse_string
 from packtype.types.assembly import Packing, WidthError
 from packtype.types.struct import Struct
-from packtype.utils import get_width
+from packtype.utils import get_width, unpack
 
 from ..fixtures import reset_registry
 
@@ -227,3 +229,56 @@ def test_parse_struct_bad_field_ref():
             """
             )
         )
+
+
+def test_parse_struct_nested():
+    """Parse a multiply-nested arrayed structure"""
+    # Declare a nested and arrayed structure
+    pkg = next(
+        parse_string(
+            """
+            package the_package {
+                // Implicit width, implicitly packed from LSB
+                struct lowest {
+                    a : scalar[2]
+                    b : scalar[2]
+                }
+                struct middle {
+                    c : lowest[2]
+                    d : scalar[2]
+                }
+                struct top {
+                    e : middle[2]
+                    f : scalar[2]
+                }
+                an_array : top[2]
+            }
+            """
+        )
+    )
+    # Unpack a value
+    the_value = random.getrandbits(44)
+    inst = unpack(pkg.an_array, the_value)
+    # Check values
+    assert inst[0].e[0].c[0].a == (the_value >> 0) & 0b11
+    assert inst[0].e[0].c[0].b == (the_value >> 2) & 0b11
+    assert inst[0].e[0].c[1].a == (the_value >> 4) & 0b11
+    assert inst[0].e[0].c[1].b == (the_value >> 6) & 0b11
+    assert inst[0].e[0].d == (the_value >> 8) & 0b11
+    assert inst[0].e[1].c[0].a == (the_value >> 10) & 0b11
+    assert inst[0].e[1].c[0].b == (the_value >> 12) & 0b11
+    assert inst[0].e[1].c[1].a == (the_value >> 14) & 0b11
+    assert inst[0].e[1].c[1].b == (the_value >> 16) & 0b11
+    assert inst[0].e[1].d == (the_value >> 18) & 0b11
+    assert inst[0].f == (the_value >> 20) & 0b11
+    assert inst[1].e[0].c[0].a == (the_value >> 22) & 0b11
+    assert inst[1].e[0].c[0].b == (the_value >> 24) & 0b11
+    assert inst[1].e[0].c[1].a == (the_value >> 26) & 0b11
+    assert inst[1].e[0].c[1].b == (the_value >> 28) & 0b11
+    assert inst[1].e[0].d == (the_value >> 30) & 0b11
+    assert inst[1].e[1].c[0].a == (the_value >> 32) & 0b11
+    assert inst[1].e[1].c[0].b == (the_value >> 34) & 0b11
+    assert inst[1].e[1].c[1].a == (the_value >> 36) & 0b11
+    assert inst[1].e[1].c[1].b == (the_value >> 38) & 0b11
+    assert inst[1].e[1].d == (the_value >> 40) & 0b11
+    assert inst[1].f == (the_value >> 42) & 0b11

From 89357ec675297a57f30c849ded6843bccb0c9f91 Mon Sep 17 00:00:00 2001
From: Peter Birch <pbirch@fractile.ai>
Date: Wed, 1 Oct 2025 11:07:52 +0100
Subject: [PATCH 2/2] Lint fix

---
 packtype/types/array.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/packtype/types/array.py b/packtype/types/array.py
index 7201639..6b476d2 100644
--- a/packtype/types/array.py
+++ b/packtype/types/array.py
@@ -3,7 +3,6 @@
 #
 
 import functools
-import inspect
 import math
 from collections.abc import Callable, Iterable
 from typing import Any, Self